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Environmental Stewardship for Farmers - 2 |
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Storage of liquid petroleum products presents a threat to public health and the environment. Liquid petroleum products include motor fuel, such as gasoline and diesel fuel, and heating fuel, such as oil or kerosene. Nearly one out of every four underground storage tanks in the United States may be leaking, according to the U.S. Environmental Protection Agency. If an underground petroleum tank is more than 15 years old, especially if it is not protected against rusting, the potential for leakage is much greater. Newer tanks and piping can leak, too, especially if they were not installed properly.
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North
Carolina
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Even a small fuel leak of one drop per second can result in the release of 400 gallons of fuel into the groundwater over the period of one year. Even a few quarts of fuel in the ground water may be enough to severely pollute a farmstead's drinking water. At low levels of pollution, water may smell or taste pure, yet be contaminated enough to harm human health. The fuel may contaminate not only your well, but the drinking water for an entire community.
Preventing tank spills and leaks is very important. Gasoline, diesel fuel, and fuel oil can move very rapidly through surface layers and pollute groundwater before the leak or spill has been noticed. Also, vapors from an underground leak can collect in basements, sumps, or other underground structures and pose risks of explosion.
Petroleum fuels contain many potentially toxic compounds. These include common solvents, such as benzene, toluene, and xylene, and additives, such as ethylene dibromide (EDB) and organic lead compounds. EDB causes cancer in laboratory animals and benzene is known to cause cancer in humans.
This publication focuses on storage of motor fuels, kerosene, and liquid heating fuels.It does not apply to liquid propane gas, since leaks vaporize quickly and do not threaten groundwater. Tanks that hold motor fuels, kerosene, and liquid heating fuels are classified as noncommercial by the North Carolina Department of Environment, Health and Natural Resources, Division of Water Quality (DWQ). If you have an underground tank which holds more than 1100 gallons, an aboveground tank of at least 660 gallons, or if the fuel in the tank is for sale, you must meet other requirements. Contact your regional office of the DWQ, shown on the map. Personnel at the DWQ can explain these regulations to you.
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This publication only applies to farm and residential underground petroleum storage tanks which hold 1100 gallons or less, or to larger tanks if they contain heating oil used on the premises for four or fewer households. The fuel in the tank must not be for sale. |
State regulations to protect groundwater apply only to tanks greater than 1100 gallons, which are classified as commercial tanks. These regulations were used as guidelines for the recommendations in this publication. For the safety of your drinking water, make every effort to meet or exceed current regulations wherever possible.
We have prepared this publication to help you focus on potential problems with your drinking water that may be caused by fuel storage tanks. Read this publication before you begin answering the questions. Gather any records you have about your fuel storage facilities. Walk in and around the area where your fuel tanks are placed. Also look at the area around your well.
Each of the following sections deals with different topics. Next to each topic is a question for you to answer. Your answers will help you to see where you have potential problems.
If you answer a question either c or d, there may be potential problems with your fuel storage and handling.
If you would like further help in assessing the condition of your fuel storage and handling, please visit your nearest Cooperative Extension Service Center and talk with your Extension agent.
If you drink water from a well or spring, the water comes from the ground. Most groundwater in North Carolina is safe to drink. If pollution gets into groundwater, your well or spring water may not be safe. Many things we all do at our homes and farms can pollute the groundwater.
If groundwater becomes polluted, it is nearly impossible to clean up. Then, the only ways to get safe drinking water are to treat the existing water, drill a new well, or get water from another source. All of these options are expensive and inconvenient.
The North Carolina Farm*A*Syst Program has a series of publications that can help you keep your drinking water safe. These publications will lead you through an evaluation of your farmstead to determine if your water is in danger of becoming or is already polluted with harmful substances from your farmstead area. If there is a problem or a potential problem, the Farm*A*Syst publications have information about how to solve the problems. The publications also list the North Carolina state agencies that can help you solve your drinking water problem.
The goal of the North Carolina Farm*A*Syst program is to help protect your families' and your health and the environment of North Carolina.
Storage Tank Location |
1. How close is your fuel storage tank to your well?It is very important that your liquid petroleum storage tank location is far enough away from your drinking water well. State well regulations, which apply to new well construction, require that commercial petroleum storage tanks be located at least 100 feet from a drinking water well. Existing wells are required by law only to meet separation requirements that were in effect at the time of well construction. For the safety of your drinking water, make every effort to meet or exceed current regulations whenever possible. Leaks from any size tank can enter the groundwater and contaminate existing wells. Tanks should also be located downslope from the well. Leaks from aboveground storage tanks can also enter the soil and contaminate groundwater. Regulations for siting aboveground storage tanks have been concerned more with preventing explosion and fires than preventing groundwater pollution. If you have an aboveground tank, follow the recommendations for underground storage tanks as a guide to prevent pollution.
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a. Tank is downslope and more than 100 feet from well. b. Tank is at grade or upslope and more than 100 feet from well. c. Tank is downslope, less than 100 feet from well. d. Tank is at grade or upslope and less than 100 feet from well; OR do not know.
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2. What is the location of your aboveground storage tank?To protect against explosion and fire, aboveground fuel tanks should be located at least 40 feet from existing buildings. Heating oil tanks attached to farm heating systems should be at least 5 feet from the building. The distance required may be more than this in some cases, depending on the type of fuel, the design and material of the tank, and the amount of fuel being stored. You should find out from your local fire official if your tank meets fire protection standards. Your local fire official may be a fire marshal, emergency management officer, or a building inspector authorized to enforce the fire code.
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2. Circle the answer that best describes the location of your aboveground tank in relation to fire protection.a. Tank was installed to fire official's recommendations. b. Motor fuel tank is at least 40 feet from any building. Heating oil tank that is part of heating system is at least 5 feet from building. c. Motor fuel tank is within 40 feet of a building, with no combustible materials close by. Heating fuel tank is outside of building. d. Motor fuel tank is within 40 feet of a building or close to combustible materials, or heating fuel tank is in basement; OR do not know. |
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3. In what kind of soil are your fuel storage tanks located?How quickly a spilled petroleum product reaches groundwater will depend upon local soils. The more porous the soil (sands and gravels, for example), the faster the rate of downward movement to groundwater. Every site has unique geologic and hydrologic conditions that can affect groundwater movement. Even though diesel fuel and fuel oil are more dense than gasoline and move more slowly through the soil, they, too, will eventually reach groundwater. The figure below illustrates potential causes of petroleum leaks that can move into and through soils.
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3. Circle the answer that best describes the soil around your tank. a. Tank is in or above fine-textured soils (silty clay, clay) with low permeability (water passes through slowly). b. Tank is in or above medium-fine textured soils (silt, silt loam, loam, clay loam, silty clay loam) with medium-low permeability. c. Tank is in or above medium-coarse textured soil (sandy clay, sandy clay loam, sandy loam) with medium-high permeability. d. Tank is in or above coarse-textured soil (sand, sandy loam, loamy sand) with high permeability; OR do not know.
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4. Is your fuel storage tank properly installed?Whenever you install a fuel storage tank, carefully follow the manufacturer's recommended practices for installation. Proper installation is one sure way to minimize the leakage potential of the tank or the piping connected to it. Even scratches in a metal tank caused by careless installation can increase corrosion and cause leaks. If you hire someone to install your tank, be sure to use an experienced, reputable installer.
A corrosion-protected underground storage tank. |
4. Circle the answer that best describes the tank installation.a. Tank was installed b. Tank was installed c. No information is available on installation. d. Tank was installed without backfill, setback, secondary |
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5. What is the type and age of your fuel storage tank?The type and age of fuel storage tanks often reflect their condition. Older steel tanks (more than 15 years old) have the greatest chance of being rusted, or corroded, and leaking. Newer tanks and piping can also leak, especially if they were not installed correctly. Corrosion protection helps keep underground steel tanks from leaking. To be protected from corrosion, a tank may have an inside liner, a protective coating on the tank and piping, or a system called cathodic protection in place. Asphalt is not a corrosion-resistant coating. Cathodic protection uses an electric current to protect the tank from the corrosive effect of soil moisture. Most older tanks do not have this protection and are at high risk for leaks. It is expensive to apply corrosion protection to existing tanks and it may be more cost-effective to replace them. New underground tanks should be installed with corrosion protection in place. Fiberglass tanks do not corrode but they are vulnerable to other risks. |
5. Circle the answer that best describes the type and age of your tank/corrosion protection. a. Tank is synthetic or protected from rust by a thick layer of noncorrosive material, or a corrosion-resistant coating and cathodic protection. b. Tank is steel, less than 15 years old, and coated with asphalt. c. Tank is coated steel older than 15 years or bare steel less than 15 years old. d. Tank is bare steel 15 or more years old; OR do not know. |
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6. What are the soil conditions near your tank?Abandoned pipes and tanks, agricultural drainage tiles, or waste materials can make it difficult to install a new tank properly. Any metal already in the ground at the tank site will increase corrosion rates for the new tank. Floodways or areas where the water table is close to the surface are poor locations for storage tanks. The water that saturates the soil can carry pollutants, including fuel, from the tank to the groundwater. Moisture can also make the tank and piping corrode faster than if they remain dry. |
6. Circle the answer that best describes the soil conditions near your tank.a. No other pipes, drainage tiles, or metal debris in the soil. Well-drained soils. Water table is always beneath tank. b. No other pipes, drainage tiles, or metal debris in soil. Moderately well-drained soils. Water table is only occasionally at tank level. c. May be metal debris in soil, or soils saturate seasonally. d. Other metal materials in soil; or poorly drained soils, often saturated; OR do not know.
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7. Is the piping from your fuel storage tanks safe?The pipes, hoses, valves, and fittings connected to a storage tank can be a major source of leaks. They are often overlooked, especially if buried underground. Piping fails because of corrosion, poor installation, accidents, and weather-related factors such as frost heaving. Piping must either be protected from rusting or be made of a noncorrosive material. Galvanized steel is not a noncorrosive material. Steel piping should have a corrosion-resistant coating and cathodic protection. Make sure that pipes cannot twist or break if the tank is bumped or disturbed. Pipes should also be sloped so that they drain back into the tank. A check valve should be as close to the dispensing point as possible to keep fuel in the line from draining onto the soil.
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7. Circle the answer that best describes the piping on your tank.a. Piping is protected from rust by cathodic protection and is coated. Pipe sloped back to tank. Check valve is at pump. b. Piping is galvanized but not coated with fiberglass or coated tank. Pipe drains back to tank. Check valve is at pump. c. Pipe is galvanized; both tank and pipe are bare. Piping is sloped back to tank, but check valve is located at tank. d. Piping and tank are both bare of dissimilar materials. The pipe cannot drain freely to the tank. All pipes are pressure pipe systems; OR do not know. |
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8. Is your tank secure from traffic?Assess traffic patterns around the tank. Determine whether the location of the tank or dispenser will block movement of vehicles. Be sure there will be no access problems if any work needs to be done on the tank. Piping should be protected from collisions with vehicles. Posts made from 4-inch steel pipe filled with concrete are a good barrier around aboveground tanks. An underground tank should not be installed in a location where vehicles will drive over it.
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8. Circle the answer that best describes the traffic around your tank.a. No vehicles in the area of the tank other than those filling the tank or being refueled; barriers keep vehicles from colliding with pump; vehicles cannot drive over underground storage tank. b. Occasional vehicles in area of tank, other than those filling the tank or being refueled; barriers keep vehicles from colliding with pump; vehicles cannot drive over underground storage tank. c. Occasional vehicles in area of tank, other than those filling the tank or being refueled; no barriers around pump; or vehicles can drive over underground storage tank. d. Other vehicles frequently moving in the area of the tank; no barriers around pump; or vehicles can drive over underground storage tank; OR do not know. |
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9. Is your tank secure from accidents?Controlling access to your gasoline and diesel pumps protects against theft and lowers pollution and fire risks. Unauthorized users can damage your tank or spill fuel. The simplest form of security is to lock your pump. For either underground or aboveground tanks, be sure the underlying soil can support the tank. For special tank locations, such as hillsides, be sure to properly anchor and hold tanks in place. Aboveground tanks can leak if they are not protected from damage by other objects. To reduce fire potential and damage to a heating oil tank in your basement, avoid using areas around or under a tank for storage. Heavy objects can also damage pipes. |
9. Circle the answer that best describes the security of your tank.a. There is a lock on the pump and it is surrounded by a six-foot locked fence. Areas around tank are free of movable objects which could damage the tank. Tank is securely anchored or in stable soil. b. There is a lock on the pump. Areas around tank are free of movable objects which could damage the tank. Tank is securely anchored or in stable soil. c. There is no lock on the pump, or areas around tank contain movable objects which could damage the tank. Tank is securely anchored or in stable soil. d. There is no lock on the pump, or areas around tank contain movable objects which could damage the tank, or the tank is not securely anchored or not in stable soil; OR do not know.
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10. Does your fuel storage tank have spill and tank overfill protection?Fuel storage tanks should have spill and overfill protection. Spill protection typically consists of a catch basin for collecting spills when the tank is filled. Overfill protection is a warning, such as a buzzer or an automatic shutoff, to prevent overflow when the tank is filled. Spill and overfill protections are important; they can prevent a number of small releases over a long period of time from polluting the groundwater. In order to prevent fuel backflow onto the surrounding land, check valves should be placed at the pump, not at the tank. Close supervision of fuel transfers is one of your best methods for protecting against spills and overfills. |
10. Circle the answer that best describes the spill and tank overfill protection on your tank.a. Tank has an impermeable catch basin plus automatic shutoff. b. Tank has an impermeable catch basin plus overfill alarm. c. Tank has an impermeable catch basin or concrete catch pad, no overfill alarm or shutoff. d. Tank has no spill or overfill protection; OR do not know. |
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11. Does your aboveground tank have the means to contain spills and any overflow that might occur?Regardless of soil conditions, locate aboveground tanks over an impermeable liner made of concrete or one of the newer synthetic materials. To decrease pollution potential, the tank should be installed inside a secondary containment structure consisting of a dike and a pad. This structure should be able to hold all of the fuel were it to leak out, with extra room for any rainfall.
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11. Circle the answer that best describes the secondary containment (for aboveground tanks only).a. Tank is placed within concrete or synthetic dike with a pad able to hold 125% of tank capacity. b. Tank is placed within dike and pad made of soil with low permeability (like clay) able to hold 125% of tank capacity. c. Tank is placed on pad. d. There is no secondary containment; OR do not know.
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12. What do you notice in the area of the tank?Your senses of sight, smell, and taste can alert you to leaks. Is there an oil-like sheen on streams or on wet places near the tank? Is nearby soil stained with petroleum? Is there a strong and constant smell of petroleum near your tank? Have you or your neighbors smelled fuel odors near plumbing or sewer line openings or in basements? If you have smelled or tasted petroleum in your drinking water, there may already be groundwater contamination, and you should contact your local health department or regional DWQ office immediately. Mechanical changes can also signal leaks or damage to the piping. Does your suction pump rattle? Does fuel flow unevenly? Does the pump hesitate too long before dispensing? |
12. Circle the answer that best describes any observable signs of leaks.a. No appearance of petroleum in surrounding soil or water; no taste or odor; pump operating normally. b. No appearance of petroleum in surrounding soil or water; pump hesitating or rattling. c. Visible sheen on soil or wet areas, or constant odor of petroleum around tank, or water in tank. d. Water tastes or smells like petroleum product; OR do not know. |
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13. Are you monitoring the tank for leaks?The tank and piping system should be tested for leaks. This is done with methods known as precision or tightness testing, or volumetric analysis. After a tank has been tested and shown not to leak, good practice requires that you regularly use a method that will detect new leaks. Your county Extension agent or DWQ representative can help you choose the right method for you. Tank tightness testing must be performed by experienced, reliable professionals. One method that is sometimes suggested involves using air pressure in the tank, then watching for the pressure to drop. Do not do this yourself. This can be hazardous if a tank has ever contained petroleum products. Too much pressure can force the product out through any leaks. Also, the air can make an explosive mixture with gasoline vapors, which can be ignited by a spark or static electricity. After the tank has been tested, measuring tank inventories is a way to help detect new leaks. EPA-approved methods for commercial tanks monitor the area around the tank for the presence of petroleum. These methods are too costly to be practical for most noncommercial tank owners. One inexpensive and easy method, manual tank gauging, involves use of a measuring stick which can be read to the nearest eighth inch. The stick is lowered to the bottom of the tank, and the level in the tank is read from the stick when it is removed. It is important not to let the stick puncture or damage the bottom of the tank. This is done twice to get an average reading, then repeated in 36 hours. Measurements must be taken at a time when no fuel is being drawn from or added to the tank. If the fuel level in the tank decreases over time when you are not withdrawing fuel, there is probably a leak. An increase in water in the tank also indicates a leak. While inventory measurement will not detect very small leaks, it will at least provide a warning that further investigation is necessary.
Manual tank guaging. The closer the tank is to the farmstead's drinking water well, the more important it is to have an adequate leak-detection system in place. Leak detection is important for all tanks because of the danger to your well water. Test the tank periodically for leaks, and measure the tank inventory regularly to help detect leaks before major problems develop. Since most tanks used on farmsteads are bare steel, tank corrosion or piping problems will cause leaks sooner or later. If your tank is more than 15 years old, or if you don't know its age, make a special effort immediately to determine whether leaks exist. Cleanup of petroleum leaks is always expensive and is rarely totally effective. This makes it important to constantly monitor underground tanks containing petroleum products. If you already have a petroleum storage tank on your farmstead, be especially aware of the age of your tank as well as the need to establish a leak-detection program. If you install a new tank, select the location carefully to be sure that your chosen leak-detection methods will be reliable and easy to use. Figure 2 shows how groundwater can be contaminated by underground tanks. |
13. Circle the answer that best describes any leak detection or tightness testing.a. Monitoring for leaks is done on a monthly (or more frequent) basis. b. Inventory control is done daily for gasoline tanks, seasonally for heating oil tanks; tank is tested for tightness annually. c. Inventory control and tank tightness testing are done occasionally. d. No regular inventory control, testing, or monitoring; OR do not know.
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14. Are there any unused tanks on your property?Tanks no longer in use can cause problems for owners and operators many years later. They will continue to corrode and, if they still contain gas or oil, will likely contaminate groundwater. Selling property with an old underground tank may also be difficult. Find out the location of any unused tanks on your property. Also, try to find out whether the tanks still contain petroleum product or have holes. These tanks must be properly closed. First, the tank must be emptied and cleaned, and then removed from the ground or filled with an inert material such as sand. If the tank is removed, it must be disposed of in a landfill or at a scrap dealer.
Notify your regional DWQ office before you have the tank pulled. You should document all steps you take to legally close your tank. This will help protect you from legal action in the event of groundwater problems. Documentation should include written records of:
Always notify your local fire department before removing a tank.
Some fire departments require that you obtain a permit first. The fire
department representative will help you be sure that precautions are taken
to prevent an explosion or other problem. Deaths have occurred due
to improper closure. What if a leak or spill has happened?If you find a leak or spill from any tank, whether it be above or below ground or even a vehicle-mounted tank, state law requires that you notify the DWQ. DWQ personnel will advise you on what actions are necessary to remedy the problem. If cleanup is required, ask for a list of contractors certified by the state to perform the cleanup. You may be eligible for reimbursement for some cleanup costs by the state Noncommercial Underground Storage Tank Cleanup Fund. This fund will only reimburse expenses that the DWQ has approved as reasonable and necessary. It will not provide reimbursement if the release of petroleum was intentional, or if it was the result of willful disregard of regulations. |
14. Circle the answer that best describes the way any unused tanks have been closed.a. Tank cleaned, emptied, and taken from ground. Surrounding soil checked for evidence of contamination, or no other tank was ever in ground. b. Tank cleaned, emptied, and filled with sand, concrete, or other inert material. Soil checked for contamination. c. Tank taken from ground or filled with inert material, soil not checked for contamination. d. Tank left in ground; OR do not know. |
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Related PublicationsPrepared by Cooperative Extension Service:
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These publications are available at your county Cooperative Extension Service Center. If you order more than one copy of the publication, there will be a small charge. Otherwise, the publications are free. You may also order these publications from Agricultural Publications, Campus Box 7603, North Carolina State University, Raleigh, NC 27695-7603. |
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Prepared by the Division of Water Quality:
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These publications can be ordered from DWQ by calling 1-919-733-8486. |
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Prepared by the U.S. Environmental Protection Agency:
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These publications can be ordered from USEPA by calling 1-573-569-7562. |
Prepared by
Dorothy L. Miner
Water Quality Extension Associate
Deanna L. Osmond
Water Quality Extension Specialist
Janet Young
Layout and Design Specialist
Adapted for North Carolina from materials produced by the National Farm*A*Syst Program, University of Wisconsin (author Pat Walsh, Department of Agricultural Engineering, University of Wisconsin-Madison and University of Wisconsin Extension, Cooperative Extension).
North Carolina's modification of Farm*A*Syst and Home*A*Syst was coordinated by Deanna L. Osmond and Gregory D. Jennings. Technical editing was provided by Judith A. Gale, and copy editing by Cathy Akroyd. Gregory D. Jennings, Richard W. Gannon, and Wilma S. Hammett were the technical reviewers at North Carolina State University.
This project has been funded with Section 319 grant monies from the U.S. Environmental Protection Agency through the N.C. Department of Environment, Health, and Natural Resources, Division of Water Quality, Raleigh, NC.
This publication was supported in part by the U.S. Department of Agriculture, Cooperative State Research, Education, and Extension Service.
Published by
NORTH CAROLINA COOPERATIVE EXTENSION SERVICE
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
4/97—5000
AG-566-2
WQWM-166
This document was updated on 9/13/00 by Janet Young.
